Dynojet A/F Meter

[brewsky]

You are probably right...."H" is just a tease....probably written down in pencil in some ancient Japanese writings hidden in the attic of a former Honda or Keihin engineer.

[teazer]

Actually it's the other way round. The correct thing to measure is fuel height. Because that's hard to measure we make do with float height and hope that the fuel height ends up OK. if floats are even slightly heavier or lighter than standard, fuel level will be off.

You can grab a spare float bowl and modify it so that there's a clear plastic tube attached and measure fuel height.

[Wilf]

Actually it's the other way round. The correct thing to measure is fuel height. Because that's hard to measure we make do with float height and hope that the fuel height ends up OK. if floats are even slightly heavier or lighter than standard, fuel level will be off.

You can grab a spare float bowl and modify it so that there's a clear plastic tube attached and measure fuel height.

I think that is exactly what I was saying.

Wilf

[brewsky]

I think we all three agree, but the question that remains for me is "what should the fuel level measurement be?"

The float height "h" measured from somewhere (gasket surface or carb body cutout) should result in the correct fuel level "H' measured from the bottom of the carb bore.

It could be directly measured with a clear tube but what should the value be?

[Wilf]

brewsky,

In my view, 'H' (the ideal and critical fuel height) is not a value that we can measure and then pass on to others with any assurance that it will be the correct 'H' for their circumstance. 'H' is the level of fuel (or as teazer notes, the height of fuel) in the bowl that will result in best engine performance.

The problem is that every engine, carburetor, operator and operating environment is different. That makes 'H' an ideal value which is tied to the individual's idea of best performance under their conditions.

In effect, that makes 'H' unobtanium to everyone other than you and your machine. That leaves everyone else at square one, making their own approximal measurements and test rides in their efforts to divine what works best.

By the way, I have searched Honda manuals and countless websites for Honda "carburetor black magic" and have yet to discover a productive link. My next search--Honda Holy Grail.

[teazer]

But that's the point. It can be measured and the actual level is no more magical than the correct float level. They are just numbers that can be adjusted.

One huge difference in the real world is that I can adjust the float tang while I'm in measuring mode, but if I measure fuel level and want to change it, I have to drain the fuel and tweak the tang, assemble, refill, measure, repeat..

I tend to use Fuel measurement when I have a persistent problem like a fuel leak or odd jetting conundrum to resolve. The rest of the time I use LM's eyeball technique. If I want to raise the level, or lower it, I used LM +1mm or LM -1mm. It's so easy to do using Ed's methodology.

BTW, used to be able to buy a set of SOHC 750 carbs, keep the bowls and throw the rest for $20 a set and that's 4 tools. Snap off the fuel overflow tube and attach clear plastic hose to the overflow tang. It's cheap and easy to do - or at least it used to be.

Setting fuel level to say 2-3mm below the gasket surface doesn't get me a perfect mixture. As Wilf noted, all it gets is fuel at a certain level which we can choose to raise or lower to change fueling until we like what we got. That revised number is less a general answer, and more an answer specific to that bike at that time.

99% of the time, the LM technique is as close as any of us needs to be.

[jensen]

Hi,

Sometimes I wonder why people are making things more difficult then they are, really I do.
I know, in the eyes of many of you I'm not the person who should say something like that, because I'm the person that holds the record to do that according to the answers I get on the forum.

By the way, I have searched Honda manuals and countless websites for Honda "carburetor black magic" and have yet to discover a productive link. My next search--Honda Holy Grail.

But how difficult can it be to read a manual ?? (I did make a copy of the page from the Honda Holy Grail , please look closely and then you have to conclude h is 26.5 mm or 1.043 in.

In my experience, this is approximately the same height when you do it as I described in my last posts, and approximately means within +/- 0,5 mm. Did you check it Brewsky ? What is your distance when measuring as I described ?

Use this basic setting to trail and error with float levels with the needle in the standard position, and let the curves from 1000 rpm to 6000 rpm tell the story.

The fuel standard level is given in the same picture (nr. 6) so what is so difficult and mystery about it ? If h is 26,5 mm, then H is 18 mm or 0.709 in. Or you could say that the fuel level is 2 mm below the float bowl gasket face.

Jensen